The importance of natural plant products as novel sources of anticancer agents is increasingly becoming evident. The benefit of using natural plant derived products is their low toxicity, multimodal action and their potential ability to enhance the immune system. With the advancement of analytical techniques we can analyze the activity of active components of these compounds that specifically target biological pathways in the cancer cell. Withaferin A (WA) is a purified product of Withania somnifera, (commonly known as Ashwagandha) and is used in many indigenous drug preparations as part of Indian ayurvedic medicine for many centuries. WA has demonstrated potent anti- cancer properties and targets several cellular pathways that result in apoptosis of tumor cells by various mechanisms. Recently it was shown to potentiate apoptosis of human pancreatic cancer cells through inhibition of HSP90 (Oh et al., 2009) as well as through up-regulation of ER stress proteins in human renal carcinoma cells (Choi et al., 2011). Additionally, it was demonstrated that crude root and leaf extracts from the parent plant stimulates T helper Type 1 (Th1) immunity by up-regulation of cytokines such as interferon gamma, induction of co-stimulatory molecules on antigen presenting cells and increased proliferation of T cells (Malik et al., 2009, Stan et al., 2009). However, nothing has been established about the mechanisms by which systemic administration of WA impacts tumor specific immunity. Our preliminary data indicates that WA causes cell death and also induces the expression of immunostimulatory proteins such as heat shock protein 70 (HSP70) in a dose dependent fashion. Expression of HSP70 in the tumor cells plays a fundamental role in the immune system by inducing tumor specific humoral and cellular immunity. Based on these results, we propose that WA can stimulate an immune mediated cancer cell death by eliciting tumor specific response by the host, through activation of innate immune cells such as dendritic cells (DCs) and subsequent stimulation of adaptive immunity. This research application will therefore focus on two goals: a) effect of WA treated tumor cells on innate immunity: dendritic cells and macrophages and b) effect of WA in tumor delay and survival in murine preclinical models (transplantable and Her-2/neu transgenic models) including whether WA can specifically target Her-2/neu tumor specific immunity. Our goal is to establish and provide evidence that natural products such as Withaferin A can be used as a chemoimmunotherapeutic agent in the treatment of Her-2/neu breast cancers. The benefit of such a strategy would impact the frequent recurrence of metastases of dormant tumor cells after conventional chemotherapy regimens that can cause tumor relapse and therapeutic failure.